---  Current Projects---

Drill Test Bench

A laboratory robotic system was designed and built that controls large hammer drills while they drill into concrete blocks. The system measures drilling speed and health related outcomes such as handle vibration, handle twist force, silica dust, and noise. The purpose is to compare drilling methods, bits and other factors on health and productivity. [Funded by CPWR and NIOSH]

Concrete Dowel Drilling


Dowel and rod drilling involves drilling holes about 1 inch in diameter 1 - 2 feet deep into concrete in order to epoxy in rebar for structural upgrades. It is usually done manually with 30-lb pneumatic rock drills and is noisy and physically exhausting work. A Universal Drilling Jig is being developed and tested at commercial construction sites in the Bay Area. The goal is to improve productivity while reducing muscle loads, vibration exposure and exposure to silica dust. The Jig has also been used at several BART construction sites for drilling holes for large anchors as well as for setting anchors.

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The Development and Application of Exposure Assessment Devices


Quantitative exposure assessment can be time consuming and expensive.  New technology such as inertial measuring units can change how we measure and monitor exposure for various applications on the job and individual level.  We are working on a variety of devices that measure, summarize and interpret physical exposures to improve how we measure, track and manage risk for MSDs.  These devices may be used to quantify job level exposures or track individual exposures for injured workers returning to work.

Biomechanical and Cardiovascular Strain in Hotel Room Cleaners

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Studies have shown that hotel room cleaners are at risk for developing MSDs based on physical and psychosocial risk factors (Krause et al 2005 & 2009).  Our lab has studied whether certain interventions such as bed lift tools and fitted sheets reduce the workload associated with making beds.   We are also interested in whether the current workload leads to cardiovascular strain placing them at risk for cardiovascular disease.

Prospective studies of Carpal Tunnel Syndrome & related Work Disability


Prospective data on 3515 production workers, followed for up to 7 years, from 50 companies were pooled from 7 research groups [UC San Francisco, SHARP, U Utah, Wisconsin U, Washington U at St Louis, U Iowa, NIOSH](Dale 2013). The study is evaluating the association of personal, sports, hobby, workplace psychosocial and workplace biomechanical factors on predicting new cases of CTS (Harris et al 2015).  Currently, research is focused on adjusting for healthy worker survivor bias and identifying whether the predictors for those with work disability from CTS differ from those associated with the incidence of CTS.

The impact of Trunk and Upper Extremity Exoskeletons on Worker Fatigue, Productivity and Comfort


Risk factors contributing to upper extremity and spine MSDs include repetition, force and awkward posture. Overhead work, defined as working at or above the shoulder, has been identified as a category of tasks with especially high risk of WMSDs, and repetitive heavy lifting increases risk for the low back.  To mitigate risk of injury, force must be decreased, the duration of the task reduced, and/or amount of rest breaks increased. Exoskeleton technology has the potential to reduce exposure to force based risk factors, aid in return-to-work programs for injured individuals, and allow an aging workforce to remain in certain occupations.  Students involved with the design of 2 different exoskeletons are testing their effectiveness in a laboratory setting.  

The Association Between Heavy Load Carrying and Women's Health in Developing Countries


Musculoskeletal injuries comprise the largest burden of disease globally.  In fact, the 1990, 2005, and 2015 Global Burden of Disease studies listed low back pain (LBP) and neck pain as the primary contributor to years lost to disability (YLD) (GBD,2015), and “among the top ten causes of YLDs in every country” (GBD,2013). Musculoskeletal injuries such as LBP affect an individual’s capacity to carry out activities of daily living (ADLs), including the ability to work and care for children.  In low- and middle-income (LMIC) countries, this can have serious implications on livelihoods and household welfare.  As in many patriarchal developing countries, “domestic load-carrying” as a low-status activity and culturally assigned to females; thus women and children bear most of the carrying burden.   Our research explores the association between heavy load carrying and musculoskeletal pain and disability among women in Tanzania and Nepal.

Physical Exposures While Performing Colonoscopies

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Gastroenterologists are at increased risk for developing recurrent thumb, hand, and elbow pain due to colonoscopy procedures.  We have evaluated forearm muscle loads and wrist postures during routine colonoscopy to understand distal upper extremity musculoskeletal risk factors associated with the 4 different subtasks of colonoscopy.  Currently we are testing various interventions to see if they reduce fatigue and discomfort among endoscopists during procedures.

Pain is NOT in the job description

A new digital story series produced in collaboration with the California Department of Public Health. Click here to see the videos.

Hand Computer Interaction Studies using Hand Gestures


The use of standard input devices such as joysticks, keyboards and hand controllers to controlling self-travel and object selection in virtual reality is challenging due to the visual requirements of interacting with such devices and the visual constraints of VR.  Thus, hand gestures used to interact with the computer will be of increasing importance to improve the usability and acceptance of virtual reality. 

Tablet Design

Tablets and smart phones are used more and more for mobile business. Can the shape and texture of tablets be changed so that they are more secure and comfortable to hold in one hand? We are testing different tablet designs to evaluate their impact on productivity, comfort, and biomechanics. In the first study, 30 experienced users tested eight tablet prototypes while forearm electromyography, upper body posture, productivity and usability were evaluated. The study findings will be useful for designers of tablets and smart phones.

Palm Rejection During Direct Touch


The primary objective of this research is to quantify the effects of palm rejection on direct touch performance, shoulder loading, and discomfort. Subjects performed a series of tasks involving one, two, and three simultaneous touches on a touch display, both with and without palm rejection. Results suggest that palm rejection affords some performance (speed) and comfort benefits, but little benefit to shoulder unloading.


Keyboard Key Spacing

Surprisingly, the spacing of keys (e.g., 19 mm) on the conventional keyboards that we all use are based on 1950's conventions and not empirical data. Keyboards with smaller key spacing may be easier for people with smaller hands to use, could reduce the size and weight of laptops, and reduce the distance to reach to the mouse. We built and tested 8 keyboards with different key spacings on 89 experienced touch typists while measuring typing speed, error, forearm muscle activity, wrist posture and subjective preference. As it turns out, you can reduce key spacing without decreasing typing speed, even for typists with large hands.

Peripheral Trackpad Size

The primary objective of this research is to quantify the effects of desktop-trackpad size on performance, posture and discomfort. Subjects performed a series of drag-and-select target acquisition tasks using three trackpads (112X63 mm to 230 X130 mm) while the dependent variables were recorded. Results suggest that trackpads with a width between 112 and 178 mm and a depth between 63 and 100 mm may provide an appropriate balance between cost, footprint, performance, and comfort.

---  Prior Projects ---

Overhead Drilling Project

Of all industries, construction has the highest rate of musculoskeletal loads to the neck, back, and upper extremity. One of the most physically demanding tasks is over-shoulder work, especially overhead drilling into concrete for the attachment of anchors, bolts, etc. in order to hang pipes, ducts, wiring, and equipment. For more information see the project Web Page. Generation four of our device is up and running.

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Computer Display Position

Because the position of a computer display affects the user's posture, eye opening, and blink rate, and hence comfort, we are investigating the relationship between display position and these measures with the aim of determining optimal display positions. Particular interests include multiple and large-area displays.

Lower Extremity Exoskeleton Reduces Back Forces in Manual Material Handling

Manual material handling remains a physically demanding task, and existing assist devices have found limited success. The project involves a lower extremity exoskeleton device which adds a restoring moment to the subject's upper body during nonneutral postures, thus reducing forces on the low back, transmitting forces directly to the ground via the exoskeleton structure. The device has been found to effectively reduce low back forces during static tests and is being evaluated in a variety of other situations. This project is being undertaken in conjunction with the UC Berkeley Human Engineering Laboratory.

Forearm Support Reduces Pain among Computer Users

A simple workstation modification, the addition of a forearm support, was found to reduce upper body pain and prevent musculoskeletal disorders among customer service workers who use a computer for more than 20 hours per week. In this randomized controlled trial, the 182 participating workers were followed for 1 year. Based on a cost-benefit analysis, employers could see a full return on the cost of providing arm boards to all employees within 11 months of the investment. The Morency rest forearm supports are manufactured by R&D Ergonomics of Maine. The study received the 2006 International Ergonomics Association/Liberty Mutual Prize.

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Computer Keyboard Studies

The effect of altering the deyboard design on hand posture, muscle load, and hand pain has been studied in laboratory and epidemiologic studies.

3D CAD Reach Zones

A CAD based shoulder load model is in development that can be used during equipment and workstation design to place frequently used objects or controls to reduce shoulder fatigue and injury risk to workers. Colored 3D reach zones, representing relative fatigue and risk are linked to a mannequin to relocate equipment elements and points of operation based on the duty cycle of the task and applied hand forces. By selecting mannequins of different anthropometries or gender, the designer can consider equipment features to accommodate a wide range of workers. 

Experimental Model for Occupational Hand Disorders

To understand the direct cause of musculoskeletal disorders or diseases of the elbow, hands, and fingers, we have developed a rabbit repetitive finger flexor model. In this model, the finger is flexed for a set number of repetitions at a predetermined frequency and force. After the flexion sessions are completed, the elbow (epicondyle), carpal tunnel, and finger joints are examined by histology and biochemistry for pathology.
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Space Station  Glove Box Design

In cooperation with the Japanese Space Agency and NASA, a new design was developed for the glove box. The glove box will be used for all biological experiments on the space station.

Carpal Tunnel Pressure

Fluid pressure within the carpel tunnel has been measured in 37 healthy people. The purpose is to identify hand postures associated with high pressures. These postures should be avoided in designing work and hand tools.

Computer Mouse and Fatigue of Long Duration Studies

A new method of measuring muscle fatigue was developed and validated. The technique was tested during extensive computer mouse use and recorded fatigue after 3 hours of mouse use.

In Vivo Tendon Force

Tendon force is measured during surgery of the hand in order to determine the relationship between fingertip force (external force) and tendon force (internal force).

In Vitro Tendon Loading

A new in vitro tendon loading system was developed to simultaneously apply different strain profiles to multiple tendons in a tissue culture environment. The system is used to evaluate the effects of precisely controlled cyclical loading on gene expression in tendons. You can watch a video article on this topic at the JOVE website.

Studies on dental tool design

Dental hygienists and dentists are at high risk for developing wrist, elbow and shoulder disorders due to poor postures and the high pinch force applied during the scraping of plaque. Dental tools of different diameter, shape, weight, and surface texture were evaluated in laboratory studies and in a 4-month randomized controlled trial of 110 dental practitioners. [Funded by NIOSH].